When a semiconductor device is manufactured, there are steps for subjecting a substrate, such as a semiconductor wafer, to various heat processes, such as an oxidation process, a diffusion process, a CVD process, and an annealing process. As one of heat processing apparatuses for performing these steps, there is used a vertical heat processing apparatus (semiconductor manufacturing apparatus) capable of thermally processing a number of wafers at a time.
This vertical heat processing apparatus includes: a heat processing furnace having a furnace opening in a lower part thereof; a lid member that hermetically seals the furnace opening; a holder (also referred to as “boat”) disposed on the lid member, the holder capable of holding a number of wafers at predetermined intervals therebetween in an up and down direction via ring-shaped support plates; an elevating mechanism that elevates and lowers the lid member so as to load and unload the holder into and from the heat processing furnace; and a substrate transfer apparatus having a plurality of support parts (also referred to as “forks”) at predetermined intervals therebetween, the substrate transfer apparatus capable of transferring (conveying) wafers between a container (also referred to as “FOUP”) capable of containing wafers at predetermined intervals therebetween and the holder. The ring-shaped support plate is used as a countermeasure for restraining or preventing a slip (crystal defect) from being generated on a peripheral portion of a wafer during a heat process of a high temperature.
As a conventional substrate transfer apparatus, there has been known an apparatus including a plurality of stopping members that are engaged with a lower surface of a peripheral portion of a wafer to support the wafer in a suspending manner. The respective stopping members can move in a reciprocating manner between a wafer support position in which a wafer is supported in a suspending manner, and a wafer disengagement position in which the supported condition of the wafer is released by the stopping members that have been moved outside an outer periphery of the wafer. The respective stopping members are driven by an actuator between the wafer support position and the wafer disengagement position in a reciprocating manner. (See, Patent Document 1).
However, in the substrate transfer apparatus, there is a problem in that a structure thereof is complicated because the stopping members, which are located on a front end side and a rear end side of a support part, are made movable. As a substrate transfer apparatus or a vertical heat processing apparatus capable of solving this problem, there has been proposed that an upside grip mechanism for supporting a wafer from above is disposed on a lower part of a fork, the grip mechanism having a fixed stopping part disposed on a front end of the fork so as to stop a front periphery of a wafer, and a movable stopping part disposed on a rear end of the fork so as to disengageably stop a rear periphery of the wafer (Patent Document 2).    Patent Document 1: 2003-338531A    Patent Document 2: 2005-311306A
In accordance with an enlarged diameter of a wafer (300 mm in diameter) and a super-enlarged diameter of a next-generation wafer (400 to 450 mm in diameter), there is fear that, in a current substrate transfer apparatus or a current vertical heat processing apparatus, a central portion of a wafer is warped by its own weight. There is also fear that the warp invites a stress on the wafer and impairs a transfer precision (it is necessary to consider a size or a space of the warp in the central portion of the wafer).